1. Field of the Invention
The present invention relates to an intelligent gas identification system and a method of gas identification for gas or volatile chemical matters in a specific environment.
2. Description of the Related Art
Conventionally, a gas concentration sensor is used for obtaining concentration for a specific gas. An example of a conventional gas concentration sensor 500 is described in detail with reference to FIG. 1a and FIG. 1b. 
The conventional gas concentration sensor 500, as shown in FIG. 1a, has a body 510, voltage input elements 520, and output elements 530. The body 510, as shown in FIG. 1b, has a substrate 512, electrodes 514, a sensing element 516, and a heater 518. Generally, the sensing element 516 is a membrane of metallic oxide, such as a membrane of tin dioxide (SnO2), which reacts to a specific gas in the vicinity of the gas concentration sensor 500. When the conventional gas concentration sensor 500 is applied in a specific environment to perform gas concentration measurement, a fixed voltage is input to the sensor 500 through the voltage input element 520 to activate the heater 518, so that the membrane of the sensing element 516 is heated to a predetermined temperature, such as 400xc2x0 C. Thus, the membrane of the sensing element 516 reacts to the specific gas to be measured in the specific environment, and the resistance of the sensing element 516 is changed due to the reaction. Then, an outgoing voltage, determined by the resistance of the sensing element 516, is obtained through the output element 530 as an outgoing signal.
It is obvious that the concentration of the specific gas in the specific environment affects the reaction, and the relation between the concentration of the specific gas and the resistance of the sensing element 516 can be established by experiment as a reference of the gas concentration sensor 500.
FIG. 2 is a chart showing an example of the gas concentration measurement with the conventional gas concentration sensor 500, in which the curves L1 and L2 respectively refer to different concentrations of the specific gas. When the voltage is input to the sensor 500 through the voltage input element 520 to activate the heater 518, the membrane of the sensing element 516 is heated to a predetermined temperature, such as 400xc2x0 C. In both cases, the resistance of the sensing element 516 is changed due to the reaction, which induced to the outgoing voltages shown as point A to concentration L1 and point B to concentration L2. It should be noted that the predetermined temperature of the conventional gas concentration sensor 500 is generally set to a preferred temperature, in which the outgoing voltage is significant, so that responses of the gas concentration sensor 500 are obvious. Fox example, the preferred temperature shown in FIG. 2 is approximately 400xc2x0 C.
The conventional gas concentration sensor 500 has a membrane-type structure, which has a relatively low cost. Further, the conventional gas concentration sensor 500 reacts to the gas to be measured in a short time and can be used effectively for a long period of time. As a result, the gas concentration sensor is widely used in various situations. For example, U.S. Pat. No. 6,336,354 discloses a gas concentration measuring apparatus, in which a gas concentration sensor is applied, that uses a heat control circuit to supply power to the heater of the sensor cyclically using a pulse-amplitude-modulated (PAM) signal. In this case, the apparatus corrects errors contained in the gas concentration signal, so that the signal is regulated, and the outgoing signal of the gas concentration sensor is significant.
However, the conventional gas concentration sensor 500 is used mainly to measure the concentration of a specific gas. It is obvious that the conventional gas concentration sensor 500 can be used in a specific environment when the specific gas exists in the specific environment. However, the membrane of gas concentration sensor 500 may react to a plurality of gases. Thus, when more than one of the gases exists in the specific environment, the conventional gas concentration sensor 500 does not distinguish between each gas, so that the outgoing signal of the gas concentration sensor 500 does not correspond exactly to a specific gas among the multiple gases, and concentrations are not obtained accurately. Additionally, when the composition of the gas in the specific environment is completely unidentified, the conventional gas concentration sensor 500 does not distinguish the composition of the gas.
In view of this, the present invention relates to an intelligent gas identification system and method thereof, in which a pulse-amplitude-modulated (PAM) signal is used as the input voltage to the conventional gas concentration sensor so that the outgoing signals corresponding to various gases differ. Thus, a chemical matter characteristics database can be established by experiment, and the chemical matter characteristics can be used as a reference fingerprint of composition and/or concentration of the gases.
The present invention discloses an intelligent gas identification system. The intelligent gas identification system has a sensor, a pulse power supply module, and a processing device. The sensor has a voltage input element, an output element and a sensing element and is disposed in a specific environment to perform gas identification. The pulse power supply module is connected to the voltage input element to send a variable pulse-amplitude-modulated voltage to the sensor through the voltage input element, so that the sensor outputs an outgoing signal through the output element. The processing device stores a plurality of chemical matter characteristics signals and receives the outgoing signal from the output element of the sensor, then compares the outgoing signal with the chemical matter characteristics signals to determine an identification result for the gas.
Further, the present invention discloses a method of gas identification. First, a sensor is provided in a specific environment. The sensor is provided with a variable pulse-amplitude-modulated voltage, so that the sensor outputs an outgoing signal corresponding to gas in the specific environment. Then, the outgoing signal is compared with a plurality of chemical matter characteristics signals to determine an identification result for the gas in the specific environment.
In the method of gas identification, the chemical matter characteristics signals can be obtained by exsposing the sensor to a plurality of predetermined chemical matters and sending a variable pulse-amplitude-modulated voltage to the sensor respectively, so that the sensor outputs each of the chemical matter characteristics signals corresponding to each of the predetermined chemical matters. Then, the chemical matter characteristics signals can be stored in a database.
In the system and method of the present invention, the outgoing signal can be a pulse amplitude voltage signal. Further, the sensing element can be a membrane of a metallic oxide, such as tin dioxide (SnO2). Further, the identification result for the gas can be composition and/or concentration of the respective constituents of the gas.